1. Field of the Invention
This invention relates to an infrared and ultraviolet radiation absorbing blue colored soda-lime-silica glass composition suitable for architectural and automotive glazing applications. The glass should have a dominant wavelength of about 485 to 492 nanometers (nm) and an excitation purity of about 3 to 18 percent. The glass is also compatible with flat glass manufacturing methods.
2A. Technical Considerations
Infrared and ultraviolet radiation absorbing colored glass substrates have a variety of different applications. In particular, such glasses may be used by architects to glaze buildings and by vehicle designers as automotive windows. Besides providing an aesthetically pleasing color, these glasses may also provide enhanced solar performance as compared to conventional clear glass.
Different materials may be added to the glass in order to provide the desired color and spectral performance. For example, iron, cobalt, nickel, selenium and titanium, to name a few, are typically added to provide the desired color composition. As materials are added to change color and enhance solar performance, care must be taken to maintain the visible light transmittance and color required for that particular application. It should also be remembered that changing the thickness of the glass will affect these spectral properties so that a particular composition which has acceptable color and performance at a particular thickness may not be acceptable at a different thickness.
One particular blue composition that provides superior spectral performance is disclosed in U.S. Pat. No. 4,792,536 to Pecoraro, et al. Commercial products which incorporate this patent are sold by PPG Industries, Inc. under the trademarks SOLEXTRA.RTM. and AZURLITE.RTM.. This glass incorporates a moderate amount of iron in the composition and has a relatively large portion of the glass in the ferrous state, expressed as FeO. In particular, the glass composition includes a basic soda-lime-silica composition and further includes 0.45 to 1 weight percent total iron (expressed as Fe.sub.2 O.sub.3). At least 35 percent of the total iron is in the ferrous state. The dominant wavelength of these glasses range from about 486 to 489 nm and excitation purity ranges from about 8 to 14 percent. From a processing standpoint, producing the glass disclosed in the patent with a high ratio of ferrous iron to total iron may require additional processing considerations not typically associated with conventional glass melting operations, as are well known in the art. However, due to the favorable acceptance of this product, it would be advantageous to be able to produce a glass having a similar color and enhanced spectral performance using conventional glass melting processing techniques.
2B. Patents of Interest
U.S. Pat. No. 3,652,303 to Janakirama Rao discloses a blue, heat absorbing glass which incorporates low amounts of iron and uses tin to convert and retain a significant portion of the iron in the ferrous state, and in particular more than 80% of the iron is retained in the ferrous state.
U.S. Pat. Nos. 4,866,010 and 5,070,048 to Boulos, et al. disclose blue glass compositions with a colorant portion consisting essentially of iron and cobalt and further including nickel and/or selenium. The glasses have a dominant wavelength of 482 nanometers (nm) .+-.1 nm and a color purity of 13% .+-.1%.
U.S. Pat. Nos. 5,013,487 and 5,069,826 to Cheng disclose blue colored glass compositions which include iron, titanium, tin and zinc as colorants. The glasses have a dominant wavelength ranging from 485 to 494 nm and a color purity of 5 to 9%.
U.S. Pat. No. 5,344,798 to Morimoto, et al. discloses a blue glass composition which includes iron, cerium, titanium, zinc, cobalt and manganese. These glasses have a dominant wavelength of 495 to 505 nm and a color purity of 5 to 9%.